1. Field
The following description relates to an acoustic wave filter device.
2. Description of Related Art
Recently, a device using a bulk acoustic wave (BAW) filter has played a very important role to enable a miniaturization, a multi-functionalization, and improvements in a performance of wireless communications systems. In order to realize characteristics of the BAW filter device, a hermetic seal capable of maintaining reliable sealing in a vacuum state so as to block the penetration of moisture is required.
As a result, among bonding technologies generally used at the time of manufacturing the BAW filter device, a wafer level bonding technology has been used to maintain the hermetic seal, including a silicon-silicon (Si—Si) direct bonding technology, a silicon-glass (Si-Glass) anodic bonding technology, and a bonding technology using flit glass.
However, these technologies are not generally appropriate for a package of the BAW filter device due to a high bonding temperature or bad workability.